Ultra violet (UV) masks are widely used in LCD manufacturing. During the sealant curing process, a UV mask is often placed in between the LCD cell and the UV light source. The mask covers an active area of the LCD, but leaves the sealant exposed to UV so it can be cured to bond a color filter (CF) glass and thin film transistor (TFT) glass together.
The purpose of the UV mask is to protect organic materials in the active area from being damaged by UV light. For example, liquid crystal can be decomposed by UV and cause bad alignment, image sticking, and other optical artifacts. These defects are commonly referred to as “mura”. UV light can also damage organic layers used on TFT and/or CF glass (e.g., negative type of photo-acrylic layer used for passivation) and cause visible artifacts on dark images. UV light may further damage the TFT devices causing artifacts or functional problems of the display.
While the UV light is blocked by the UV mask, it is also reflected by the UV mask. As such, UV light reflected from the LCD on which sealant is being cured may further be reflected by the UV mask and onto UV sensitive portions of the LCD resulting in defects. Conventionally, a thick boarder around the LCD has helped to minimize the effects of the UV reflections and/or to prevent the UV light from reaching the UV sensitive portions of the LCD.